The critical path method (CPM) is a comparatively recent engineering development particularly adapted for use in the construction industry for the planning and scheduling of construction acitivities. For a detailed analysis of CPM, reference is made to the book entitled, CPM IN CONSTRUCTION MANAGEMENT, Second Edition, by James J. O'Brien, published by McGraw-Hill Book Company, Copyright 1971.
In construction projects there are activities which may be scheduled to start at certain events (times) and end at other events later on. An acitivity is a work item leading from or to an event; and an event is a point of time for completion or starting or an activity. In the CPM method, the activities are usually drawn on a chart indicated by lines or arrows and which start or terminate where two or more activities meet.
The engineers responsible for the particular scheduling of a project usually have a network chart of events and activities made up beforehand which is based on estimates. When reports from the field are received after the project has started, this network chart is examined regularly (which may be daily or weekly) to determine the progress of the entire project and of its individual activities, which is noted on the chart. If a critical activity is behind schedule, the Project Manager may employ additional resources (e.g. personnel or equipment), and from the chart he can tell whether the entire schedule has to be updated in order to complete it on time. This is a tedious job; and quite a complex one in situations where the project is complex.
In the invention hereof, a monitoring apparatus which will be described in detail hereinafter is provided whereby the project engineers or management in charge of the project may at a glance determine the status thereof so that they may take appropriate action when required.